Implement search_regex from #847
implement fallbacks and defaults in _search_regex
print WARNINGs during test + minor fix to NBAIE
raise exceptions on warnings during tests - and solve a couple of them
use search_regex in new IEs
XHamster: Can't see the description anywhere in the UI
print "please report this issue on GitHub" on every ExtractorError
do not ask the user to report network errors
_html_search_regex with clean_html superpowers
test: extend the reach of info_dict checking

* print the info_dict in a format suitable to easy adding to tests.json during tests if un-tested fields are detected
* make it possible to put the crc32 in tests.json if the field is too long
* complete the "info_dict" fields in existing tests
* fixed the bugs catched doing this
switch long info_dict fields checking to md5
YoutubePlaylistIE: get *all* videos

For that, we add parameter safeSearch=none that asks youtube not filter
results before sending them to us.

Note: this parameter could be added to YoutubeSearchIE and YoutubeUserIE
as well, but I don't know what would be the impact in term of unwanted
results. Maybe expose that as a parameter? For a playlist it's different
since the user chose what she put in the playlist.
Add GametrailersIE
Fix HypemIE test: the song name has been changed
use _search_regex in GenericIE
Merge branch 'search_regex' - PR #872 - closes #847
add _search_regex to the new IEs
Fix GooglePlusIE: the video_page url has changed of place
Merge pull request #887 from anisse/master

Fetch all entries that are in a youtube playlist

Also add a test.
Ignore invalid dates (Fixes #894)